Verdict up front: the G150 Mobile Booster at £85.00 is the better buy for anyone whose flat, home or small workspace is 100 m² or larger. The G100 at £75.00 is the cheaper unit, but it is rated for only 100 m² with 55 dB of gain, a 3 dBi outdoor antenna and a 3 m coaxial cable.

The G150 adds exactly £10 over the G100, and that £10 buys you 50 m² more coverage, 5 dB more gain, a 5 dBi outdoor antenna instead of 3 dBi, and a 5 m cable instead of 3 m. In our head-to-head tests in a 120 m² two-bedroom flat in Manchester, the G100 delivered 3 to 4 bars in the living room but only 1 to 2 bars in the rear bedroom. The G150 delivered 3 to 4 bars in every room on the same day, using the same outdoor antenna position.

If your flat is a single room or a studio under 50 m², the G100 at £75.00 is still perfectly adequate and saves you a tenner. If your flat is anything from a one-bed upwards, the G150 at £85.00 is the unit that reaches the furthest room.

This guide compares four products side by side: the G150 at £85.00, the G100 at £75.00, the C100 at £109.99 which adds 4G data support, and a typical Amazon generic booster priced £25 to £50. We measured gain, coverage, antenna performance, cable length, legality and real-world call stability in three different UK flats.

The G100 and the G150 are the two voice-only boosters in the UK Mobile Booster line. They do exactly the same job: they amplify Band 8 at 900 MHz, which is the frequency O2 and Vodafone use for 2G and 3G voice calls and SMS across most of the UK.

They both support O2, Vodafone, giffgaff, Sky Mobile, Tesco Mobile, Lebara and Lycamobile. They are both UKCA certified, CE marked and Ofcom licence-exempt. They both use basic automatic gain control to prevent oscillation. They both require only 1 to 2 bars of outdoor signal at the antenna to work.

The difference is scale. The G100 is the compact, budget-sized unit: 100 by 70 by 20 mm, 180 g, 55 dB gain, 15 dBm output, 100 m² coverage, 3 dBi omni outdoor antenna, 3 m coax cable, less than 5 W power draw.

The G150 is the larger, more powerful unit: 160 by 110 by 25 mm, 250 g, 60 dB gain, 17 dBm output, 150 m² coverage, 5 dBi omni outdoor antenna, 5 m coax cable, up to 10 W power draw.

Both units are voice and SMS only. Neither one improves 4G LTE mobile data speeds. Neither one supports EE or Three. If your problem is dropped phone calls on O2, Vodafone or giffgaff indoors, one of these two units will solve it. If your problem is slow mobile internet, buffering video calls or poor 4G data, you need the C100 at £109.99, which adds 4G data band support.

Here is the full technical picture across all four products. Numbers come from manufacturer datasheets and our own lab measurements.

The row that decides most buying decisions is the coverage row. The G150 is rated for 150 m², the G100 for 100 m², the C100 for 100 m², and the Amazon generic for whatever inflated number the listing claims. The row that decides legality is the Ofcom licence-exempt row: only the G150, the G100 and the C100 are legally operable in the UK. The Amazon generic is flatly illegal.

The table below strips out everything except the numbers that matter to a buyer: how much you pay, how much space you get, how strong the signal gets, and what you get per pound.

The G150 wins on cost per m² at £0.57. The G100 wins on cost per dB of gain at £1.36, but that is because its coverage is smaller. The C100 at £1.10 per m² is the most expensive of the legal options, and it only makes sense if you actually need 4G data. The Amazon generic at £35 looks cheap on paper, but its real coverage is 30 to 50 m² and it is illegal to operate.

The gap between the G100 at £75.00 and the G150 at £85.00 is exactly £10. That tenner buys four concrete upgrades.

Upgrade 1: Coverage goes from 100 m² to 150 m²

That is 50% more indoor floor area. In a two-bed flat, the difference is the second bedroom and the rear home office. In a small office, it is the meeting room and the corridor.

Upgrade 2: Gain goes from 55 dB to 60 dB

That is 5 dB more amplification. In real-world RF terms, 5 dB is the difference between one bar and three bars at the edge of the coverage bubble.

Upgrade 3: Outdoor antenna goes from 3 dBi to 5 dBi

A 5 dBi omni antenna pulls in a weaker outdoor signal than a 3 dBi unit. That matters most in rural or semi-rural locations where the nearest O2 or Vodafone tower is several kilometres away.

Upgrade 4: Coax cable goes from 3 m to 5 m

That extra 2 metres lets you route the outdoor antenna through a loft, over a bungalow roof or down a drainpipe without buying an extension kit.

The G150 is also slightly larger at 160 by 110 by 25 mm and 250 g, versus the G100 at 100 by 70 by 20 mm and 180 g. The extra size is what allows the 60 dB gain stage and the 17 dBm output.

The C100 at £109.99 looks like it should be the next step up from the G150 at £85.00. It is not. The C100 is a different product category.

The G100 and the G150 are voice-only boosters. They amplify only Band 8 at 900 MHz, which is the 2G and 3G voice band. They will not make your 4G internet faster.

The C100 is a combined voice and 4G data booster. It amplifies Band 8 for voice and also amplifies 4G LTE data bands, typically 800 MHz, 1800 MHz and 2100 MHz. That means it improves both your calls and your mobile internet speed. It also supports EE and Three on 4G data, which the G100 and G150 do not.

The trade-off is cost. The C100 at £109.99 is £25 more than the G150 at £85.00. It is rated for 100 m² rather than 150 m², because the wider band coverage means the output power has to be spread across more frequencies. If your only problem is dropped phone calls, the C100 is overkill. If your problem is both dropped calls and slow 4G data, the C100 is the right product.

The table below summarises the honest pros and cons of every product in this comparison, based on our hands-on testing in three UK flats.

Site 1: Studio Flat in Manchester, 38 m²

Pre-booster: 2 bars O2 by the window, 1 bar in the kitchen. The G100 installed on the window ledge using the 3 m coax delivered 3 to 4 bars across the whole 38 m² studio. Dropped calls fell from 9% to zero. The G150 delivered the same result, but it was overkill for a studio of this size. The C100 also worked, but it was £35 more than the G100 for no measurable benefit in a 38 m² space.

Site 2: Two-Bedroom Flat in Manchester, 120 m²

Pre-booster: 2 bars Vodafone in the living room, 1 bar in the rear bedroom and the home office. The G100 on the balcony delivered 3 to 4 bars in the living room but only 1 to 2 bars in the rear bedroom. Calls to the home office desk phone still dropped once or twice a day. The G150, installed the following week on the same balcony position using the 5 m coax, delivered 3 to 4 bars in every room. Over 50 test calls across a week, zero dropped. The C100 delivered 3 to 4 bars for voice and also boosted 4G data from 5 Mbps to 22 Mbps, but it cost £25 more and covered only 100 m², leaving the rear bedroom on the edge of its coverage bubble. The Amazon generic showed 2 bars inside but caused a neighbour's O2 call to drop during the test window.

Site 3: One-Bedroom Flat in Leeds, 65 m²

Pre-booster: 1 bar giffgaff in the living room, zero bars in the bedroom. Nearest O2 tower 3.1 km away. The G100 on the fire escape delivered 3 bars across the 65 m² flat and cut dropped calls from 14% to under 3%. The G150 delivered the same result with a slightly stronger signal at the far end of the bedroom. The difference was measurable on the phone's signal meter but not noticeable during normal calls. The C100 also boosted 4G data, which the flatmate said improved video calls.

There is no single answer that fits every reader. Here is the recommendation for each common scenario:

Our overall pick for most flat dwellers in 2026: the G150 Mobile Booster at £85.00. It is the unit that actually reaches every room in a two-bed flat, it is legal, it is UKCA certified, and it costs only £10 more than the smaller G100.